1. Field of the Invention
The present invention relates generally to a rotor of a rotating electric machine and, more particularly, to a rotor of an alternating current (AC) generator or motor in which the rotor includes a pair of pole core members having a plurality of claw-shaped magnetic poles extending along an axial direction of the rotor at regular intervals around the rotor, wherein the claw-shaped magnetic poles are directed face to face from the individual pole core members and engaged with one another as if surrounding a rotor coil.
2. Description of the Background Art
A construction of a rotor of a conventional rotating electric machine is shown in Japanese Laid-open Patent Publication No. 2001-86715, for instance. According to the Publication, the rotor includes a rotor coil and a pair of pole core members having a plurality of claw-shaped magnetic poles extending like claws along an axial direction of the rotor at regular intervals around the rotor. The rotor is constructed by fitting the pole core members on a rotary shaft with the claw-shaped magnetic poles of the two pole core members directed face to face from front and rear sides and engaged with one another so that the claw-shaped magnetic poles surround the rotor coil, wherein a magnet which produces a magnetic field oriented in a direction opposite to the direction of a magnetic flux formed between two adjacent claw-shaped magnetic poles is located between side surfaces of the oppositely directed two adjacent claw-shaped magnetic poles. The rotating electric machine (AC generator or motor) includes the rotor thus constructed and a stator located to surround the rotor, the stator including a stator core on which a stator coil is wound, as illustrated in the aforementioned Patent Publication.
When the pole core members are excited by the rotor coil in this construction, the claw-shaped magnetic poles on one side are magnetized as north (N) poles and the oppositely directed claw-shaped magnetic poles on the other side are magnetized as south (S) poles. As the magnets which produce magnetic fields oriented in directions opposite to the directions of the magnetic fluxes formed between the adjacent claw-shaped magnetic poles are situated between the side surfaces of the oppositely directed adjacent claw-shaped magnetic poles, the number of lines of magnetic fluxes between the side surfaces of the adjacent claw-shaped magnetic poles is decreased and the number of lines of magnetic fluxes extending from outer peripheral surfaces of the claw-shaped magnetic poles toward the stator is increased.
One construction proposed in the aforementioned patent Publication No. 2001-86715 employs reinforcing members having a generally M-shaped cross section for holding magnets on both side surfaces of each claw-shaped magnetic pole. Another construction proposed in the Publication employs reinforcing members having a generally C-shaped cross section for holding magnets on both side surfaces of each claw-shaped magnetic pole. In either of these constructions, the magnets are held at fixed positions on the side surfaces of the claw-shaped magnetic poles by the reinforcing members against a centrifugal force acting on the magnets due to rotation of a rotor, because the reinforcing members are hooked on the inside of the claw-shaped magnetic poles.
As shown in the foregoing discussion, the rotor of the conventional rotating electric machine (AC generator or motor) includes a pair of pole core members having multiple claw-shaped magnetic poles extending like claws along the axial direction of the rotor at regular intervals around the rotor, in which the pole core members are fitted on the rotary shaft with the claw-shaped magnetic poles of the two pole core members directed face to face from front and rear sides and engaged with one another so that the claw-shaped magnetic poles surround the rotor coil. The magnets which produce the magnetic fields oriented in the directions opposite to the directions of the magnetic fluxes formed between the two adjacent claw-shaped magnetic poles are situated between the side surfaces of the adjacent claw-shaped magnetic poles with the magnets supported by the reinforcing members. In this construction, the magnets supported by the reinforcing members are separated from the side surfaces of the claw-shaped magnetic poles when the rotor is at rest. When the rotor turns, exerting a centrifugal force on the magnets, the magnets go into tight contact with the side surfaces of the claw-shaped magnetic poles. The magnets supported by the reinforcing members are caused to go into contact with and come apart from the side surfaces of the claw-shaped magnetic poles with rotary motion of the rotor in this fashion.
In the rotor of the conventional rotating electric machine thus constructed, each of the claw-shaped magnetic poles is narrowed and thinned toward an extreme end, forming an inclined surface on its inside. This construction of the prior art has a problem that the centrifugal force acting on the magnets and vibrations occurring as a result of rotation of the rotor could cause the reinforcing members holding the magnets to shift toward the extreme ends of the claw-shaped magnetic poles, creating a gap between the magnets and the side surfaces of the claw-shaped magnetic poles and consequently causing the magnets to deviate from their normal positions.
This invention has been made to provide a solution to the aforementioned problem of the prior art. Specifically, it is an object of the invention to provide a rotor of a rotating electric machine in which magnets located between side surfaces of adjacent claw-shaped magnetic poles of a pair of pole core members are held stationary on the side surfaces of the claw-shaped magnetic poles regardless of changes in rotating speed of the rotor or recurring cycles of its rotary motion and stoppage.
According to the present invention, a rotor of a rotating electric machine includes a rotary shaft, a rotor coil surrounding the rotary shaft, a pair of pole core members having a plurality of claw-shaped magnetic poles extending like claws along an axial direction of the rotor at regular intervals around the rotor, each claw-shaped magnetic pole becoming thinner toward its extreme end forming an inclined inside surface facing the rotary shaft and the pole core members being fitted on the rotary shaft with their claw-shaped magnetic poles directed face to face from front and rear sides and engaged with one another so that the claw-shaped magnetic poles surround the rotor coil, a plurality of magnets located on both sides of each claw-shaped magnetic pole such that each of the magnets produces a magnetic field oriented in a direction opposite to the direction of a magnetic flux formed between the adjacent claw-shaped magnetic poles, a plurality of magnet mounting members for holding the magnets against both side surfaces of each claw-shaped magnetic pole, and a backup ring having an outer peripheral surface for securing the magnet mounting members in position.
Having a generally C-shaped cross section, each of the magnet mounting members includes magnet retaining portions formed on both sides for holding the magnets against the side surfaces of each claw-shaped magnetic pole, and a middle portion having a flat platelike shape which matches the inclined inside surface of each claw-shaped magnetic pole, each of the magnet mounting members and the magnets fitted in the magnet retaining portions on both sides together forming a magnet assembly. The claw-shaped magnetic poles of the pole core members each have a stopper portion at the extreme end on the inclined inside surface, and the magnet assembly is fixedly mounted on each claw-shaped magnetic pole with the middle portion of the magnet mounting member placed against the inclined inside surface of each claw-shaped magnetic pole and engaged with its stopper portion.
The outer peripheral surface of the backup ring is so shaped as to align with alternately oppositely inclined inside surfaces of the magnet mounting members of the magnet assemblies mounted on the claw-shaped magnetic poles at their basal parts, and the backup ring is fitted inside the magnet assemblies mounted on the claw-shaped magnetic poles such that the backup ring aligns with the inclined inside surfaces of the magnet mounting members.
In this construction, the magnet assembly and the magnets fitted therein are prevented from being displaced toward the extreme end of each claw-shaped magnetic pole due to a centrifugal force acting on the magnets of the magnet assembly as a result of rotation of the rotary shaft, and the individual magnet assemblies are held tight against the claw-shaped magnetic poles by the backup ring. This construction makes it possible to produce a rotor of a rotating electric machine in which neither the magnet assemblies nor the magnets fitted therein come off or deviate from their normal positions.
These and other objects, features and advantages of the invention will become more apparent upon reading the following detailed description in conjunction with the accompanying drawings.